This invention relates to wafer carriers. More particularly it relates to sealable wafer enclosures having doors with latching mechanisms.
Various methods have been utilized for enclosing wafers in containers. For such storage and shopping some containers have rigid bodies with vertical slots for receiving the wafers and with flexible snap-on covers. These containers are generally not suitable for use in applications where the wafers are not to be exposed to the ambient atmosphere.
For wafers in the range of 200 mm and smaller, containers known as SMIF (standardized mechanical interface) pods 20 such as shown in FIG. 1, have been utilized to provide a clean sealed mini-environment that allows transfer of wafers into processing equipment without exposing the wafers to the ambient atmosphere. Examples of these pods are shown in U.S. Pat. Nos. 4,532,970 and 4,534,389. Such SMIF pods typically utilize a transparent container portion 34 with a lower door frame portion 35 configured as a flange defining an open bottom 52 and a latchable door 36 that closes the open bottom. The door frame portion 35 clamps onto processing equipment and a door on the processing equipment attaches to the lower SMIF pod door. Both doors may be simultaneously lowered downwardly from the shell into a sealed processing environment in said processing equipment. A separate H-bar carrier 38 positioned on the top surface 40 of the SMIF pod door 36 and loaded with wafers is lowered with the pod door for accessing and processing said wafers.
The semiconductor processing industry has moved toward utilization of larger wafers, specifically 300 mm wafers. Transport modules for such wafers, by way of developing industry standards, utilize a front opening door that drops downwardly from the module. Referring to FIG. 2 such a front opening enclosure is shown. Such an enclosure has analogous components within the container portion 34 without a separate removable carrier.
Conventional configurations of door enclosures and latching mechanisms for sealable enclosures are known in the art. Generally, these typically have the disadvantage that they are not easily disassembled, they have numerous moving parts, and they utilize metallic parts including fasteners. The use of metallic fasteners or other metal parts is highly undesirable in semiconductor wafer carriers or containers. Metallic parts generate highly damaging particulates when rubbed or scrapped. Assembly of a module with fasteners causes such rubbing and scrapping. Thus, the use of metal fasteners or other metal parts in wafer enclosures is to be avoided.
Although enclosures as described above are utilized in relatively clean environments, such enclosures will over time accumulate contaminants on the enclosure, in the enclosure, and in the interior of the door enclosure ultimately requiring cleaning. Such contaminants may be created by the rubbing of parts such as the operation of the door latching mechanism as described above, by the wafers being loaded and unloaded on the wafer shelves, and by the door being engaged and disengaged with the container portion. The numerous parts in conventional latching mechanisms, the difficulty of disassembly of the doors, and the use of metallic fasteners make the cleaning of such doors difficult. Easily disassembleable doors, with easily disassembleable latching mechanisms, and with minimal moving parts are highly desirable.
The larger doors required for larger wafer carriers require secure latching mechanisms in the doors. Ideally, such mechanisms will be mechanically simple with few moving parts and no metal parts.
Recently front opening transport modules have been developed that satisfies many of the above requirements. See, for example, U.S. Pat. No. 5,915,562 to Nyseth and Krampotich and assigned to the owner of the invention of this application. Also see Ser. No. 08/904,660, in which the issue fee has been paid, to Eggum, Wiseman, Mikkelsen, Adams, and Bores, also assigned to the owner of the invention of the instant application. The '562 patent and allowed 08/904,660 application are incorporated by reference herein. These latching mechanisms, as well as the other wafer carrier latching mechanisms known in the art, will typically use rotatable cammed members. These cammed members have typically been formed of generally circular plastic plates with elongate recesses defining cam surfaces.
In prior art carriers such latching mechanisms were enclosed within door enclosures. Such enclosures generally will isolate and contain any particle generation created by the latching mechanism. Such particles can accumulate and eventually need removal and cleaning. Traditionally, wafer carriers including wafer containers are cleaned with water solutions and dried with pressurized air or gases. Such cleaning is critical in keeping yields up. In order to effectively accomplish cleaning, the doors need to be disassembled or at least have covers removed exposing the latching mechanisms. This process is labor intensive and tedious. To the extent the cover is not removed, access and cleaning of the interior is difficult. Also if washing is accomplished with the latching mechanism enclosed, drying of the enclosed latching mechanism is problematic.
The rotatable cammed members are particularly useful in conforming with the industry standards for robotically opening the 300 mm carrier doors. See SEMI E62, Provisional Specification for FIMS Door, available from the Semiconductor Equipment Manufacturers Institute, Mountain View, Calif., and attached as an Appendix. These standard requires the use of two parallel spaced tools, termed “latch keys” which are robotically inserted into a door. Both tools are simultaneously rotated clockwise to unlatch the door. Consistent with these standards, conventional front opening transport modules or shippers for 300 mm wafers utilize two separate latching mechanisms, one for each side of the door.
Such mechanisms that are also manually openable, utilize handles that also turn the internal cammed member. Traditional 300 mm shippers that have such manual handles require each of two such handles to be separately rotated and then the door is manually removed by pulling on the manual handles. Such separate rotational movement by each hand of an operator in non symmetrical, awkward, and generally counterintuitive. Additionally it is difficult to ascertain if each rotational handle has been turned the full necessary rotation for full latching or unlatching.
Although such rotating cammed members function in wafer carrier doors, they have several deficiencies. The rotatable cammed member can be difficult to design and fabricate and they typically require relatively large circular cammed members for reasonable mechanical advantage. Reducing the size of such cammed members reduces the mechanical advantage. Moreover cammed members do not typically have smooth operation when translating the rotational motion to a linear motion that is irregular as is appropriate in latching and unlatching applications. Particularly, when manually rotating such rotating cammed members, false stops may occur before the latch portions are fully extended or retracted.
Moreover, such cammed rotatable members are inimical to providing a supplemental non-rotational manual grasping latching/unlatching handle. Providing rotating supplemental manual handles are known. However, such handles that rotate provide a very insecure handling means which can lead to non-smooth cumbersome manual placement and removal of doors from the door openings of the enclosure portions. Such non-smooth operation can lead to inadvertent contact between the door and enclosure at the door opening causing scrapping with particle generation, disruption of seating of the wafers, particle launching from the carrier, or other undesirable consequences. A wafer door with a latching mechanism would ideally have grasping handles that manually operate the latching mechanism that are non-rotating.
A manually operated door that is smoothly, easily and intuitively operated and that has a simple mechanical design is needed. Moreover, such a door is needed that complies with the industry standards for robotic operation of the door.